Optical fiber couplers in office and area distribution systems typically are made by breaking the fiber and fusing or otherwise bonding the cleaved ends to a pre-made coupler. An alternative coupling method is to extract signal energy through the fiber's cladding while the fiber is active or inactive. In this approach, the signal-containing fiber is bent, thereby allowing a traction of the signal energy to escape through the cladding; and that energy is collected by a detector. An example of this method is described in the patent of Beals, et al, U.S. Pat. No. 4,557,550, issued Dec. 10, 1985.
Many commercial fiber distribution networks are subject to high change and rearrangement rates. In these networks, if the fiber splicing regime requires the severing of one or more fibers for each new coupler, an eventual cumulative transmission degradation is introduced, which in commercial distribution networks is highly disadvantageous. As the optical fiber network is extended more and more widely into commercial offices, therefore, the spliced-in coupler method of extending the optical fiber network is increasingly unattractive.
The fiber coupling techniques which involve bending the fiber offer an inherently more attractive way to wire and grow a commercial optical fiber installation, because of the relatively lower risk of contamination and cumulative degradation. The prior art bending techniques, however, almost invariably subject the fiber to a high stress which itself introduces degradation and thus defeats the advantages of the technique.